Regional differences between male colour patterns suggest there may be distinct populations or subspecies (Norman 2003). Individuals from the east and southern coast show both genetic and morphological differences that suggest previous isolation and subsequent secondary contact to form a continuous distribution (Reid et al. 2005). It has been suggested that the Spencer Gulf population may represent a separate species (Bronwyn Gillanders pers. comm. 2010).

Justification:Sepia apama has been assessed as Near Threatened. Intense fishing in one location has resulted in massive local population declines. Although this has had limited impact across the species range, it is coupled with the potential (but not evidence/occurrence so far) for intense localized fishing elsewhere, albeit on smaller aggregations. Because the species is short-lived (one to two years) and semelparous, the impact of such fishing would likely be catastrophic and we therefore consider this species Near Threatened (as it almost qualifies for a threatened listing under criterion A3d). We believe that a population reduction of greater than 20% may occur in the future based on existing exploitation of the largest known breeding aggregation and potential future exploitation of other smaller breeding aggregations elsewhere along the coast. If the population in the upper Spencer Gulf is shown to be a separate species then the Spencer Gulf species would be assessed as Endangered.

This species is endemic to Australia (Reid et al. 2005). Its range stretches across southern Australia to Pointes Cloates in Western Australia to Shoalwater Bay in Queensland (Reid et al. 2005). It is also found around Lord Howe and Norfolk Island (Reid et al. 2005).

Countries occurrence:

Native:

Australia (Lord Howe Is., New South Wales, South Australia, Victoria, Western Australia)

The population size of this species is unknown. Estimates of abundance and biomass at the spawning aggregation area in northern Spencer Gulf, South Australia show a 57% decline between 2001 and 2008 (Hall 2008) and this is assumed to be the result of intense fishing activity in this area. This spawning aggregation, which is easily detected by divers and exploited by fishers, is associated with the physical features of the Gulf itself. Compared with the open coast, the water is relatively sheltered and the Gulf has plenty of hard substrate providing good attachment sites for eggs. The only other subpopulation for which information is available is Wollongong. The information from this area is anecdotal and comes from albatross researchers (the albatross feed on the spawning aggregations of cuttlefish). In the Wollongong region, aggregations also appear to be dependent on the availability of suitable habitat. The S. apama seaward distribution boundary appears to be determined by water depth, and is estimated at about 75 metres. The coastal strip between Red Point (Pt Kembla) and Austinmer appears to be the area where S. apama is most concentrated (total area 70-80 m²). It is suspected that this is due to the nature of the sea bottom, as this area has numerous reefs, which are not typical of the sea floor to the north and south of the region. The number of S. apama carcasses and bones observed at sea does vary from year to year, but a maximum estimate is several thousand (cumulative annual total). Smaller concentrations of S. apama occur at other locations, including Sussex Inlet and Ulladulla, which are south of Wollongong. It is unknown what proportion of the total population the Spencer Gulf breeding aggregation represents but, in terms of area, the Spencer Gulf IMCRA province encompasses about 15 % of the total shelf provinces inhabited by S. apama. Hence, if the population size elsewhere has remained stable, and the breeding aggregation in Spencer Gulf is only drawn from Spencer Gulf, then the total population decline to date is equivalent to about 8.5 %.

This species is a neritic species that occurs in a variety of habitats including: coral reefs, rocky reefs, seagrass beds and muddy and sandy areas (Norman 2003). They are active by day preying on fish and crustaceans (Norman 2003, Reid et al. 2005). During breeding, ritualized visual displays are observed (Norman 2003). After mating the large eggs are laid in crevices and take three to five months to hatch at low temperatures (12°C) (Reid et al. 2005). The distribution of this species may be restricted to cool southern waters because low temperatures reduce the problems associated with gas exchange in large eggs (Reid et al. 2005). The young develop directly (Norman 2003). The adults are preyed upon by dolphins, particularly during the spawning season (Norman 2003) and albatrosses (H. Battam pers. comm.). They appear to spawn in aggregations based on suitable habitat for egg laying.

This species is collected as bycatch as well as by hook-and-line, and spear fisheries along the southern Australia coast (Reid et al. 2005). It has been actively targeted since the mid 1990s. The fishery in the Upper Spencer Gulf is of particular concern. There is also concern that smaller aggregations (such as that found at Wollongong) might be fished in the future.

Ocean acidification caused by increased levels of carbon dioxide in the atmosphere is potentially a threat to all cuttlefish. Studies have shown that under high pCO2 concentrations, cuttlefishes actually lay down a denser cuttlebone which is likely to negatively affect buoyancy regulation (Gutowska et al. 2010). This species is the target of commercial fisheries (e.g. Spencer Gulf, Norman 2003), which have reduced population size by 57% in the Spencer Gulf. It is also taken by hook-and-line or spear fishing and as bycatch off southern Australia (Reid et al. 2005). The Spencer Gulf population is additionally suffering from threats imposed by a proposed desalination plant development at Point Lowly. This may lead to high levels of salinity in Spencer Gulf, higher temperatures, increased turbidity levels, decreased oxygen levels and possibly the discharge of contaminants, which would likely reduce the Spencer Gulf population even further. Unpublished data suggest from the Geelong area suggest a two year pre-breeding harvest could eliminate the whole population. Local fisherman report that in March-April S. apama embark on a pre-breeding feeding frenzy. They attack hooked fish and are detached with much difficult when brought to the surface. Within this period, they would appear to be extremely vulnerable to fishing. Hence, the greatest threat to this species is probably intense localised fisheries on breeding aggregations (albeit smaller than the Spencer Gulf aggregation) around the coast.

Recent fishing activity targeting the mass spawning aggregations at Spencer Gulf caused a decline in numbers leading to a temporary closure of the fishing grounds (Norman 2003). These mass spawning areas are easily accessible and could be used as tourist attraction (Norman 2003). Further research is recommended to determine the population trends, distribution, life history traits and threats impacting this species.